1. Field of the Invention
This invention relates generally to real-time simulator image display including earth terrain simulation and, more specifically, to a method and system for generating databases used in real-time image displays including real-time simulators.
2. Description of Related Art
Real-time geo-specific terrain visualization has become an increasingly important requirement for military as well as commercial simulation endeavors. It is critical to be able to quickly generate accurate, realistic terrain databases for battlefield and flight simulators. During offensive operations, the military may use these simulators to plan and create the sequences of events that occur during a mission before an actual battle. Also, flight training for commercial and military pilots is significantly improved when simulators have updated information concerning the area where the pilots actually fly and the airfields where they take off and land.
Traditionally, these terrain databases are generated manually using a visual database design system (VDBDS). The person utilizing the VDBDS must specify the input data sources including satellite and aerial imagery, digital elevation data, vector shapes used to define roads, rivers and other boundaries, and 3-D models of buildings and other ground features. This process is quite costly and time consuming. Once the input sources have been identified, the database modeler must then configure numerous VDBDS options that control how the input data will be processed and ultimately define the fidelity of the output database. The database modeler must ensure an appropriate balance between fidelity and performance such that the target simulation platform can process the database in real-time. Once the VDBDS has been configured, it must then process all of the input sources by combining them into merged database with the modeler-specified characteristics. The merged database contains polygons and texture in varying levels of detail (LODs). The visual simulation system loads and utilizes this merged database at run-time through a process generally known as “database paging”. Patented examples of this approach include SmartMesh™ developed by Terrain Experts and ROAM (Real-time Optimally Adaptive Mesh) developed by The University of California.
There are numerous significant drawbacks with the above approach. The processing time required by a typical VDBDS to produce a large area database can be on the order of days or weeks, requiring dedicated CPU resources and resulting in databases that require far more disk space than the source data they are produced from. If new data becomes available (e.g. updated aerial imagery of a target area collected by a reconnaissance mission) then the database modeler must reconfigure the VDBDS to utilize the new data. Once reconfigured, the VDBDS must then reprocess the input data, requiring days or weeks before the results can be visualized.
Another significant disadvantage to the above approach is that the resulting databases do not automatically scale with hardware advancements. Modern graphics hardware performance doubles approximately every six months [ref]. In order to take advantage of the fidelity afforded by improved graphics capabilities, a database modeler must reconfigure the VDBDS to produce more detailed output. As the output detail increases, so does the time required by the VDBDS to process the source data, as well as the size of the resulting database.
Large databases tax system resources such as CPU time and disk access at run time. This limits the practical extent of databases produced using the approach described above. Furthermore, because all processing must be performed prior to run-time, the entire database must be produced offline. For large-area databases, many of the resulting database LODs may never actually be visualized and are therefore wasted. Finally, the quality of the database generated is entirely dependant upon the skill of the database modeler, making it necessary to have an expert on hand for updating the visual databases.
Because of these limitations, a need exists to overcome the problems with the prior art, and particularly for a system and method which combines proven tools and algorithms with freely available data to create a worldwide database generation system.